JP4702491B2 - Organic electroluminescence device - Google Patents

Description

  The present invention relates to an organic electroluminescence display element having a high luminance and a large area.

  An organic electroluminescence display element, which is one of flat panel displays, has a structure in which an organic light emitting medium is sandwiched between an anode and a cathode, and light emission occurs when an electric current is passed. As the light-emitting medium, a laminate of a plurality of organic layers is usually used. Since it is a self-luminous type, it has features of high brightness, high viewing angle, and low driving voltage.

  As the organic electroluminescence display element, a matrix structure in which a plurality of anode lines and a plurality of cathode lines are crossed is used. A first electrode line is formed on the substrate, and at least a second electrode line is formed so as to intersect the first electrode line across the light emitting medium. When the first electrode is an anode, the second electrode is a cathode, and when the first electrode is a cathode, the second electrode is an anode. One organic electroluminescence single element is formed as a pixel at the intersection of each electrode line (see FIG. 5), and the luminance of the pixel is controlled by energizing the corresponding electrode line.

  By the way, although the above-mentioned low drive voltage is advantageous in a small organic electroluminescence display element, it is not necessarily advantageous in a large organic electroluminescence display element. Rather, since the area is large, a large current is required. In the large current drive, not only the drive circuit becomes large, but also a voltage drop and power consumption due to wiring resistance become large, which is a problem.

  Furthermore, the organic electroluminescence display element has a problem of an element short circuit due to a defect. Since organic electroluminescence display elements have a thin film structure, there are many cases where short circuits are caused due to defects such as small dust. Then, the pixel does not emit light and becomes a black spot. This is particularly noticeable when the pixel structure is rough.

JP-A-8-202287

  As described above, in a display device having a conventional structure, when the area is large, a large current drive is required, and the adverse effect due to the wiring resistance is increased. In addition, the pixel may not emit light due to an element short circuit due to a defect, and display quality may be significantly deteriorated.

  The present invention has been made to solve these problems, and an organic electroluminescence element that suppresses the adverse effect of wiring resistance by suppressing the driving current to a minimum and minimizes the deterioration of display quality due to a short circuit of the element. It is to provide.

In order to solve the above-described problems in the present invention, a first aspect of the present invention provides a plurality of organic electroluminescence devices in which a light emitting medium is sandwiched between a first electrode and a second electrode and formed adjacently on the substrate A first electrode having a single element, the first electrode being a transparent electrode formed as an isolated pattern for each organic electroluminescence single element, and a first electrode for supplying a current to the first electrode main part has a wiring, the light emitting medium is formed on said first electrode principal part on, said second electrode and the second electrode main portion made of a metal that will be formed so as to connect the isolated pattern next to the light emitting medium If and a second electrode wiring, an organic electroluminescent device organic electroluminescence single elements are connected in series, said first electrode main part is formed on a substrate, the light emitting medium is formed And a connection portion connected to the second electrode, a portion of the second electrode is laminated on the connection portion, the first electrode, and the second electrode and the electrode are connected by said connecting portion, said first electrode wiring is an organic electroluminescent device characterized in that it possess an auxiliary electrode.

  According to the present invention, since the pixel is divided into a plurality of single elements and connected in series, even if some of the single elements are short-circuited, other single elements are alive, so that damage is minimized. Can be fastened. In addition, the drive current can be suppressed to reduce the adverse effect of the wiring resistance.

According to a second aspect of the present invention, in the organic electroluminescent element according to the first aspect, the second electrode main part and the second electrode wiring are formed of the same metal .
According to a third aspect of the present invention , in the organic electroluminescent element according to the first or second aspect, the auxiliary electrode is made of a metal .
According to a fourth aspect of the present invention, there is provided the organic electroluminescent element according to any one of the first to third aspects , which is driven at a constant current.

  According to the organic electroluminescence display element of the present invention, since the pixel is divided into a plurality of single elements and connected in series, even if some single elements are short-circuited, other single elements are alive, Damage can be kept to a minimum. In addition, the drive current can be suppressed to reduce the adverse effect of the wiring resistance.

  Consider a case where a pixel of a matrix type organic electroluminescence display element is divided into n single elements and connected in series (ignoring the gap). The drive voltage for obtaining the same luminance is n times, but the drive current is 1 / n. In the case of an organic electroluminescence display element, the original driving voltage is as low as several volts, so even if it becomes n times, it does not become a big burden. The advantage of being able to reduce the current is greater than that. Further, even when a short circuit occurs at one location, (n−1) / n of the light emission area is maintained.

  Hereinafter, the present invention will be described in detail according to the manufacturing process with reference to FIGS. First, an insulating substrate 1 is prepared, and a first electrode line 2 is formed thereon. The 1st electrode line 2 can be divided into the main part 2a which forms a pixel, and the wiring 2b which supplies an electric current on a role. In the present invention, the first electrode main portion 2a is formed as a plurality of isolated patterns (see FIG. 2A). As the substrate 1, a glass substrate, a plastic substrate, or the like can be used. In the case where the first electrode is an anode, a transparent electrode such as ITO (indium tin composite oxide), indium zinc composite oxide, or zinc aluminum composite oxide can be used as the anode.

  Next, the insulating layer 3 is formed. The insulating layer 3 has an opening in the isolated pattern group portion of the first electrode (see FIG. 2B). The opening corresponds to the light emitting part 3A and the connecting part 3B. As the insulating layer 3, an inorganic insulator such as silicon oxide, silicon nitride, and aluminum oxide, or an organic insulator such as a photoresist can be used. The first purpose of the insulating layer 3 is to insulate the wiring 2b of the first electrode and the wiring 5b of the second electrode. The second purpose is to establish the light emitting part and to suppress the deterioration caused by the electrode edge part to extend the life. When wiring is performed separately as will be described later, the insulating layer 3 may be omitted.

  Subsequently, the light emitting medium 4 is formed in a predetermined portion including the light emitting portion of each isolated pattern. (See FIG. 2 (c)). As the luminescent medium 4, for example, a laminated structure such as a hole injection layer / hole transport layer / light emitting layer or a hole injection layer / light emitting layer / electron transport layer is used.

  As the hole injection / transport layer, metal phthalocyanines such as copper phthalocyanine and tetra (t-butyl) copper phthalocyanine and metal-free phthalocyanines, quinacridone compounds, 1,1-bis (4-di-p-tolylaminophenyl) Cyclohexane, N, N′-diphenyl-N, N′-bis (3-methylphenyl) -1,1′-biphenyl-4,4′-diamine, N, N′-di (1-naphthyl) -N, Aromatic amine-based low molecular hole injection / transport materials such as N′-diphenyl-1,1′-biphenyl-4,4′-diamine, and polymer hole transport materials such as poly (para-phenylene vinylene) and polyaniline, It can be selected from polythiophene oligomer materials and other existing hole transport materials.

  As the light-emitting layer, 9,10-diarylanthracene derivatives, pyrene, coronene, perylene, rubrene, 1,1,4,4-tetraphenylbutadiene, tris (8-quinolinolato) aluminum complex, tris (4-methyl-8- Quinolinolato) aluminum complex, bis (8-quinolinolato) zinc complex, tris (4-methyl-5-trifluoromethyl-8-quinolinolato) aluminum complex, tris (4-methyl-5-cyano-8-quinolinolato) aluminum complex, Bis (2-methyl-5-trifluoromethyl-8-quinolinolato) [4- (4-cyanophenyl) phenolate] aluminum complex, bis (2-methyl-5-cyano-8-quinolinolato) [4- (4- Cyanophenyl) phenolate] aluminum complex, tris 8-quinolinolato) scandium complex, bis [8- (para-tosyl) aminoquinoline] zinc complex and cadmium complex, 1,2,3,4-tetraphenylcyclopentadiene, pentaphenylcyclopentadiene, poly-2,5-di Heptyloxy-para-phenylene vinylene, coumarin phosphor, perylene phosphor, pyran phosphor, anthrone phosphor, porphyrin phosphor, quinacridone phosphor, N, N′-dialkyl-substituted quinacridone phosphor, Naphthalimide-based phosphors, N, N′-diaryl-substituted pyrrolopyrrole-based phosphors, and the like can be mentioned, and these can be used alone or mixed with other low-molecular materials or polymer materials.

  As the electron transport layer, 2- (4-biphenylyl) -5- (4-t-butylphenyl) -1,3,4-oxadiazole, 2,5-bis (1-naphthyl) -1,3 , 4-oxadiazole, oxadiazole derivatives, bis (10-hydroxybenzo [h] quinolinolato) beryllium complexes, triazole compounds, and the like.

  These can be formed by a vacuum evaporation method or a coating method such as dip coating, but since patterning is required, a mask evaporation method, that is, a method of performing vacuum evaporation through a mask is preferable. The total film thickness of the luminescent medium is 1 μm or less, preferably 50 to 150 nm.

  Thereafter, the second electrode line 5 is further formed. At that time, the second electrode main portion 5a is formed so as to be connected to the adjacent isolated pattern from above the light emitting medium (see FIG. 2D). Further, the shape is long along the longitudinal direction of the second electrode wiring 5b, and the corners are rounded. These have the effect of increasing the strength against the tension in the longitudinal direction of the second electrode wiring 5b, and enable patterning with good reproducibility. When the first electrode is an anode, the second electrode is a cathode. As the cathode, a single metal such as Mg, Al, or Yb can be used. Alternatively, a compound such as Li, oxidized Li, or LiF is sandwiched by about 1 nm at the light emitting medium interface, and Al or Cu having high stability and conductivity is laminated and used. Alternatively, in order to achieve both electron injection efficiency and stability, one or more metals such as Li, Mg, Ca, Sr, La, Ce, Er, Eu, Sc, Y, and Yb having a low work function and stable Ag, An alloy system with a metal element such as Al or Cu is used. For example, MgAg, AlLi, CuLi or the like. The thickness of the cathode is preferably about 10 nm to 1 μm.

  The second electrode line can be formed by a mask vapor deposition method. The mask pattern of the second electrode main part is long along the longitudinal direction of the mask pattern of the second electrode wiring, and the curvature radius of the mask pattern of the second electrode main part is 1/10 or more of the width. In the vapor deposition mask pattern for forming the second electrode line, the mask pattern of the main part of the second electrode is long along the longitudinal direction of the mask pattern of the second electrode wiring, and the radius of curvature is large. The strength against the tension in the longitudinal direction can be increased, and patterning can be performed with good reproducibility.

  Note that the mask pattern of the second electrode main part is long along the longitudinal direction of the mask pattern of the second electrode wiring, and the dimension in the direction parallel to the wiring is related to the shape of the vapor deposition mask hole of the second electrode main part. Means longer than the dimension in the direction perpendicular to Further, the curvature radius of the mask pattern of the second electrode main portion being 1/10 or more of the width means that the curvature radius of the sharpest portion is 1 which is the shortest diameter with respect to the shape of the vapor deposition mask hole of the second electrode main portion. / 10 or more (that is, the corners are rounded). These are not limited to rectangles with rounded corners, and may be elliptical, for example.

  As a result, the pixel portion is composed of a plurality of organic electroluminescence single elements, which are connected in series (see FIG. 1). The connections can be in series, in parallel, or a combination thereof, but series is effective for the following reasons. For example, if the current is in series, the current can be kept small, and voltage drop due to wiring resistance, heat generation, and current load of the driver can be reduced. Second, even when a short circuit of an organic electroluminescence single element occurs, the influence on other single elements is small, and damage can be minimized. This is based on the fact that the majority of organic electroluminescent single element failures are short circuits.

  In the case of constant current driving, the brightness of the other single elements remains unchanged, and the brightness decreases by the area ratio of the short-circuited single elements. That is, the influence of the short circuit on the other is small.

  In the case of constant voltage driving, the voltage corresponding to the short-circuited single element is assigned to other single elements, and the luminance increases, which works in a direction to cancel out the area reduction. That is, as long as the number of short-circuited single elements is small, the pixel luminance change can be further reduced. However, when the number of short-circuits increases, the voltage per single element increases, and there is also a drawback that it becomes easier to break down.

  In order to prevent deterioration of the element, a sealing layer or a sealing container can be provided. These are useful for preventing element deterioration due to moisture and oxygen.

  Further, in order to reduce the electrical resistance of the first electrode wiring 2b and the second electrode wiring 5b, a metal such as Cu, Al, Ti or the like can be provided as an auxiliary electrode (see FIG. 3). Alternatively, the first electrode and the second electrode can be formed only in the vicinity of the pixel, and all the wiring between the pixels can be made of metal wiring (see FIG. 4).

  When a color filter layer of RGB is formed below the transparent electrode and a white light emitting medium is used, a full color display is obtained. Alternatively, a full color display can be formed using an RG fluorescence conversion filter and a blue light emitting medium.

  Needless to say, the first electrode can be used as a cathode and the second electrode can be used as an anode.

  First, an ITO layer was formed as a transparent conductive film on the glass substrate 1 by sputtering. Further, in order to improve transparency and conductivity, heat treatment was performed in air to crystallize ITO. Next, ITO was patterned by photolithography and wet etching to form the first electrode line 2 (see FIG. 2A).

  A photosensitive resin was applied / prebaked thereon, and the insulating layer 3 was formed by exposure / development / postbaking. The insulating layer 3 has openings corresponding to the light emitting part 3A and the connecting part 3B (see FIG. 2B).

  Further, a hole injection layer / hole transport layer / light emitting layer was formed as the light emitting medium 4 on the opening (light emitting portion) 3A. The hole injection layer is copper phthalocyanine, the hole transport layer is N, N′-di (1-naphthyl) -N, N′-diphenyl-1,1′-biphenyl-4,4′-diamine, and the light emitting layer is tris. It was an (8-quinolinolato) aluminum complex, and was vapor-deposited by 20 nm, 60 nm, and 70 nm, respectively (see FIG. 2C).

  And Al was mask-deposited as the 2nd electrode line 5 (refer FIG.2 (d)). At that time, the mask pattern of the second electrode main portion 5a was a pattern that was long and rounded in the longitudinal direction of the mask pattern of the second electrode wiring 5b. Specifically, the length was 8 mm, the width was 2 mm, and the corner radius of curvature was 0.2 mm. A plurality of organic electroluminescence single elements were completed by the second electrode line 5 and simultaneously connected in series. When a pattern long in the direction perpendicular to the longitudinal direction of the second electrode pattern was used as a mask or a pattern with a small radius of curvature, deformation due to tension was remarkable, and it was not suitable for use.

  Finally, germanium oxide was formed as a sealing layer (not shown).

  A pulse current drive test was conducted, and it was confirmed that the voltage at the same luminance was about n times and the current was about 1 / n times (in this case, n = 3). In addition, a long-time driving test confirmed that black spots due to short circuits are limited to single pixels and that damage can be minimized.

It is explanatory drawing which shows the principal part of the organic electroluminescent display element of this invention. It is explanatory drawing which shows the manufacturing process of the organic electroluminescent display element of this invention. It is explanatory drawing which shows another example of the organic electroluminescent display element of this invention. It is explanatory drawing which shows another example of the organic electroluminescent display element of this invention. It is explanatory drawing which shows the conventional organic electroluminescent display element.

DESCRIPTION OF SYMBOLS 1 ... Board | substrate 2 ... 1st electrode line 2a ... 1st electrode main part 2b ... 1st electrode wiring 3 ... Insulating layer -3A ... Opening (light emission part)
-3B ... opening (connection part)
4 ... luminescent medium 5 ... second electrode line 5a ... second electrode main part 5b ... second electrode wiring

Claims (4)

A light emitting medium is sandwiched between a first electrode and a second electrode on a substrate, and has a plurality of organic electroluminescent single elements formed adjacent to each other on the substrate , the first electrode being the organic electroluminescent single element A first electrode main portion comprising a transparent electrode formed as an isolated pattern for each and a first electrode wiring for supplying a current to the first electrode main portion, and the luminescent medium is disposed on the first electrode main portion. is formed, said second electrode and a second electrode main portion and the second electrode wiring formed of a metal that will be formed so as to connect the isolated pattern next to the light emitting medium, the organic electroluminescence single element An organic electroluminescence element connected in series, wherein the first electrode main part is formed on a substrate, a light emitting part on which the light emitting medium is formed, a connection part connected to the second electrode, Equivalent to Has a range, a portion of the second electrode is stacked on the connecting portion, closed and said first electrode, and said second electrode are connected by the connecting portion, said first electrode wiring is an auxiliary electrode An organic electroluminescence device characterized by comprising: The organic electroluminescence device according to claim 1, wherein the second electrode main part and the second electrode wiring are formed of the same metal . The organic electroluminescence device according to claim 1, wherein the auxiliary electrode is made of a metal . It is constant current drive, The organic electroluminescent element in any one of Claims 1-3 characterized by the above-mentioned.

Images